For a purpose of reducing manufacturing processes of a highly integrated semiconductor device, collective processing of a stacked film is required in which a plurality of films made of an insulating material and a plurality of films made of an electrically conductive material are stacked alternately.
During this processing, the selectivity of etching for the conductive films of the stacked film can be ensured by using a mask made of silicon oxide (SiO2). However, the selectivity of etching for the insulating films of the stacked film is difficult to be ensured.
One countermeasure against the problem is to increase the thickness of the mask made of silicon oxide. However, if the thickness of the mask is made larger, processing of the mask becomes more difficult, and the processing time becomes longer.
Furthermore, if a mask made of metal is used, etching may be inhibited by reaction products during etching. Moreover, metallic contamination may occur.